The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

"Nowhere near enough was done" to stop Sean Price reoffending in the days before he murdered Melbourne schoolgirl Masa Vukotic, a judge has said.

Handing down a life sentence to Price, Justice Lex Lasry said "catastrophic mismanagement" led to Price being out on bail when he was clearly a danger to the community.

"There were many red flags to indicate that the risks of leaving you to your own devices were very significant and likely to involve violence, but nowhere near enough was done," Justice Lasry told the Victorian Supreme Court this morning.

Masa Vukotic.

"This is a tragic case."

Justice Lex Lasry said Price was not impaired or psychotic when he killed the 17-year-old in a park in the Melbourne suburb of Doncaster.

The life sentence means a minimum of 38 years without parole, but there is no guarantee he will be released after that time.

Price will be 70 when he becomes eligible for parole in the year 2054.

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The court heard that Price, 32, set out from his home on March 17 last year with the intention of murdering someone.

He packed an extra T-shirt because he predicted his first would become covered in blood.

Price chose to go to a park in the affluent suburb of Doncaster because of his hatred of rich people.

He told police he had picked out Masa because she was dressed like a "yuppie".

Sean Price covers his face as he is led into court today. (AAP)

"She's like started talking to a bird like f---ing Snow White," Price told detectives.

"I just had to kill her."

Masa was stabbed 49 times in the brutal attack, which took place while Price was out on bail for another crime.

Price then went on a crime spree, culminating in the violent rape of a woman in her workplace, motivated by the belief he was "going to jail forever".

The day before Sean Price murdered Melbourne schoolgirl Masa Vukotic, corrections officials noted he was "hostile, agitated and staring intently".

During sentencing the judge said Price was an example of the mismanagement of either the Corrections process or the Parole Board, saying the fact that he was left unattended in the community is "extraordinary".